Synthetic Metals 160 (2010) 2476–2480 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Yellow–green organic light-emitting diode based on tris(2-methyl-8-quinolinolate) scandium Marina A. Katkova ∗ , Tatyana V. Balashova, Alexander A. Maleev, Vasilii A. Ilichev, Alexey N. Konev, Georgy K. Fukin, Alexander S. Mitin, Sergey Yu. Ketkov, Mikhail N. Bochkarev G.A. Razuvaev Institute of Organometallic Chemistry of RAS, Tropinina 49, Nizhny Novgorod, 603950, Russia article info Article history: Received 14 April 2010 Received in revised form 21 September 2010 Accepted 24 September 2010 Available online 18 October 2010 Keywords: Scandium complex 2-Methyl-8-quinolinolate amidine Electroluminescence Non-doped OLED Hole-transporting DFT calculations abstract Efficient yellow–green electroluminescence emission at  max = 530 nm with CIE coordinates x = 0.3913, y = 0.4947 was obtained with organic light-emitting devices based on tris(2-methyl-8-quinolinolate) scandium (1). The device with the configuration of indium tin oxide/N,N ′ -bis(3-methylphenyl)-N,N ′ - diphenylbenzidine/1/Yb exhibits current efficiency of 3.1 cd/A and power efficiency of 1.8 lm/W at a luminance of 100 cd/m 2 . The DFT calculations demonstrate that structural changes of the scandium com- plex 1 influence the electroluminescence spectrum, the better agreement with experimental data being achieved when monodentate ligands are taken into consideration. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Recently the main attention has been attracted on the appli- cation of metal complexes as electroluminescent materials for organic light emitting diodes (OLED) [1]. Many research groups have focused on the preparation of efficient light emitting com- pounds based on known classes of main-group, transition-metal and lanthanide coordination complexes [1–9]. Complexes of rare earth metals with organic ligands present an astounding class of emissive materials for OLEDs due to peculiarities of their lumi- nescence properties [4–11]. They have similar chemical properties and various emission spectra. Among these rare earth complexes the electroluminescent scandium compounds represent the effi- cient ligand-centered emitters [12,13]. On the other hand, Sc complexes could be used as simple model systems for theoreti- cal investigations of lanthanide derivatives. Recently we reported the electroluminescent properties of scandium 8-quinolinolate complex using the non-doped simple OLED devices [14,15]. The performances of these devices were significantly enhanced as com- pared with those of analogous device with the Alq 3 emitting layer, which is commonly used as a standard. Particular interest has been ∗ Corresponding author. Tel.: +7 831 4354021; fax: +7 831 4627497. E-mail address: marina@iomc.ras.ru (M.A. Katkova). paid to the influence of the substituents at the C2 position of the 8-quinolinolate ligand on the electroluminescent properties. To fol- low up on the discovery of electroluminescent properties of tris(2- methy-8-quinolinolate)scandium (1) we fabricated the simple non-doped two-layer OLEDs with the structures of ITO/HTL/1/Yb, using N,N ′ -bis(3-methylphenyl)-N,N ′ -diphenylbenzidine (TPD) or amidine (AMD) as a hole-transporting layer (HTL). To date, TPD has proven to be one of the most efficient hole-transporting materials. However, it is well known that TPD has a tendency to crystal- lize at elevated temperatures, causing device degradation. Herein we present our efforts to design a new hole transporting mate- rial based on amidine derivatives. Two-layer device ITO/TPD/1/Yb based on tris(2-methy-8-quinolinolate)scandium has shown effi- cient yellow–green emission at  max = 530 nm with CIE coordinates x = 0.3913, y = 0.4947. 2. Experimental 2.1. General 2-Methyl-8-quinolinol, 1-naphthonitrile, isopropylamine, N,N ′ -diphenyl-N,N ′ (di(m-tolyl)benzidine (TPD) and commercial Yb (99,9% trace metal basis) were purchased from Sigma–Aldrich. All manipulations were carried under vacuum using standard Schlenk techniques. The scandium complex Sc[N(SiMe 3 ) 2 ] 3 was 0379-6779/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2010.09.030